The purpose of this investigation is to perform cell kinetic studies "in vitro" of scleroderma and normal fibroblasts. Skin biopsies will be obtained from involved and non-involved skin from scleroderma patients. Additional controls will consist of normal fibroblasts. Explants from both, dermis and the subcutaneous tissue will be placed in culture dishes using the standard clot technique. Cellular outgrowth will be monitored daily with an inverted microscope until a primary monolayer is obtained. Doubling time will be estimated by the cell count technique. Morphology of normal and scleroderma fibroblasts will be studied during the log and stationary phase by means of regular histology and electron microscopy. Fibroblasts will be incubated with tridiated thymidine and mitotic index will be determined. Explants of involved and non-involved skin will be incubated with 14C proline for 1, 6, 12 and 24 hours. The specimens will be studied by light and electron microscopy autoradiography. The pathology and electron microscopy of 63 cases of scleroderma is under current investigation.